Hướng dẫn trả lời:
a) `(x + 2)^2 - 2.(x^2 - 4) + (2 - x)^2.`
`= (x + 2)^2 - 2.(x + 2).(x - 2) + (x - 2)^2.`
`= [(x + 2) - (x - 2)]^2.`
`= (x + 2 - x + 2)^2.`
`= 4^2.`
`= 16.`
b) `(2a + 3b)^2 + (4a - 6b).(2a + 3b) + (2a - 3b)^2.`
`= (2a + 3b)^2 + 2.(2a + 3b).(2a - 3b) + (2a - 3b)^2.`
`= [(2a + 3b) + (2a - 3b)]^2.`
`= (2a + 3b + 2a - 3b)^2.`
`= (4a)^2.`
`= 16a^2.`
* Câu c bạn thiếu mũ 2, mình sửa lại đề nha.
c) `(a - b + c)^2 + (c - b)^2 + 2.(a - b + c).(b - c).`
`= (a - b + c)^2 + 2.(a - b + c).(b - c) + (b - c)^2.`
`= [(a - b + c) + (b - c)]^2.`
`= (a - b + c + b - c)^2.`
`= a^2.`
* Đề câu d thiếu nên mình sửa lại nha.
d) `3.(2^2 + 1).(2^4 + 1).(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= (2^2 - 1).(2^2 + 1).(2^4 + 1).(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= [(2^2)^2 - 1^2].(2^4 + 1).(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= (2^4 - 1).(2^4 + 1).(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= [(2^4)^2 - 1^2].(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= (2^8 - 1).(2^8 + 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= [(2^8)^2 - 1^2].(2^16 + 1).(2^32 + 1) - 2^64.`
`= (2^16 - 1).(2^16 + 1).(2^32 + 1) - 2^64.`
`= [(2^16)^2 - 1^2].(2^32 + 1) - 2^64.`
`= (2^32 - 1).(2^32 + 1) - 2^64.`
`= [(2^32)^2 - 1^2] - 2^64.`
`= (2^64 - 1) - 2^64.`
`= 2^64 - 1 - 2^64.`
`= -1.`
